Effects of saponin extracts from Solanum elaeagnifotium fruits on ion uptake by clover seedlings

Abstract

Solanum elaeagnifolium Cav. fruits contain high concentrations of steroidal saponins. Treatment of 3‐day‐old clover seedlings with aqueous fruit extracts modified Ca2+ uptake without significantly altering K+ and H2PO4− uptake. The extracts increased Ca2+ uptake in the concentration range of 0.2 to 20 mM Ca2+. Uptake curves could be represented by two phases. In the lower phase (0.2‐1.0 mM Ca2+), this change could be related to an increase in Vmax. Pretreatment of seedlings with saponin extracts significantly reduced ATP‐dependent Ca2+ uptake and Ca2+‐dependent ATPase activity in a fraction isolated from root homogenates by centrifugation at 1500 g for 15 min. Saponins purified from S. eleagnifolium extracts by thin‐layer chromatography modified in vitro the Ca2+‐ATPase activity of this fraction, indicating that the steroid may act directly on Ca2+ transport across membranes.